This invention relates to the field of radio frequency identification tags and the use of such RFID tags within a tag interrogating and feedback system for real time tracking and data transfer with such tags for product monitoring along a product distribution flow path within a product distribution web.
There exists many attempts in the prior art to remotely uniquely identify product items and to collect, collate and process such product identifiers so as to provide a centralized reporting and tracking capability over such product items when widely distributed.
For example, applicant is aware of U.S. Pat. No. 5,289,372 which issued to Guthrie et al on Feb. 22, 1994 for a Global Equipment Tracking System. Guthrie teaches an attempt to keep track of the changing configurations of individual computers tied to a central data base by means of modem communication. The product items being tracked are in fact the various hardware units which configure each computer. Each hardware unit has associated therewith a sensor. Each sensor is hardwired to a collector for each computer. The collector for each computer transmits its configuration information, based on input from the sensors, when interrogated via modem communication by a host computer. The problems associated with tracking individual product items which are being quickly distributed along distribution paths within a distribution web are not addressed.
Applicant is also aware of U.S. Pat. No. 4,636,950 which issued Jan. 13, 1987 to Caswell et al for an Inventory Management System Using Transponders Associated With Specific Products. Caswell discloses the use of radio frequency transponders on relatively expensive to purchase items which may spend relatively long periods of time at a dealer""s location where, for example, motorcycles or automobiles may be sold. Caswell teaches the use of short range radio transponders built into each product so as to uniquely identify each product, upon interrogation by a fixed interrogation transponder at the dealer""s location, with a unique identification code preinstalled into random access memory in the product transponder. A host or central computer system, via modem communication to computers at the dealer""s locations, relay commands that trigger the dealer""s interrogator transceivers to interrogate the transponder equipped products in the dealer""s inventory using, sequentially, each of the serial numbers of the products which have been shipped to that dealer and which are not known to the host computer system to have left the dealer""s inventory. It is taught that in, for example, sufficiently large showroom areas, to use a multiplicity of interrogatory transceivers. It is also taught that interrogations by the interrogator transceivers are repeated at least in cases where unusual responses are encountered, to observe consistency and permit overcoming a limited amount of noise interference. It is further taught that an interrogator transceiver might be placed with its antenna field covering an exit or entrance into a merchandise storage area so as to check that properly scheduled product units are exiting or entering. The inherent limitations in such xe2x80x9cchoke-pointxe2x80x9d interrogations are in part recognized in that Caswell states that in cases such as factory or warehouse exits where it is desired to monitor a large number of units in limited interrogation time, the use of ambiguous codes transmitted by the interrogating transceiver or the use of different operating frequencies may allow for unique identification of different product items or groups of such items such as brands or types of merchandise. The solution to the problem of the choke-point interrogation such as taught in the present invention is not suggested.
Applicant is also aware of U.S. Pat. No. 5,671,362 which issued to Cowe et al on Sep. 23, 1997 for Materials Monitoring Systems, Materials Management Systems And Related Methods. Cowe teaches the inventory tracking of items that will fit on a sensor equipped shelf. The shelf sensors may detect items by the presence of the item""s weight upon the shelf. It is also taught that each product packaging will include a label which is machine readable, the label being, for example, bar code, magnetic, holographic or radio-emitting so as to provide for identification and tracking of the product. It is also taught that the sensing systems may include three dimensional movement detection systems employing infrared, ultrasound, optical, radio wave or otherwise signaling techniques accompanied by suitable processing such as ranging or imaging to determine the inventory status of stored items on the shelf. The problems actually associated with unique identification and tracking using radio frequency transponders, which it is one of the objects of the present invention to address, are not taught nor suggested, and nor are the solutions.
Applicant is also aware of U.S. Pat. No. 5,266,925 which issued Nov. 30, 1993 to Vercellotti et al for an Electronic Identification Tag Interrogation Method. Vercellotti discloses a method of retrieving unique tag identification signals when multiple signals are received upon electronic interrogation at a portal. Upon receipt of more than one reply by the interrogator at the portal, the interrogation address is bisected and retransmitted, and subsequently again bisected and retransmitted until a single response is isolated. The method is then repeated to isolate and identify the remaining tags. The handling of choke-point interrogation and multiple replies such as employed in the present invention is neither taught nor suggested.
With respect to the use of environmental sensors, such as temperature sensors cooperating with RFID tags, in the prior art it is known to use temperature loggers not associated with real time communication of the data to remote interrogators. Prior art temperature loggers are electronic or mechanical devices that record temperature over a time period. Temperature loggers used in prior art mobile applications do not have communications links to aid in automation and therefore require significant human intervention. That is, in the prior art, it has been impossible to fully automate the temperature logging process. The data contained in a temperature logger needs human intervention to extract its log. Sometimes, depending on the design of the logger, the logger needs to be sent away to be processed, the results being returned in electronic or paper format. Because of the human intervention, monitoring, as a real-time event, and automatic log retrieval and analysis are not possible.
In summary, the method and apparatus of the present invention for identification and monitoring of, and obtaining data relating to, products moving along a distribution path includes at least one radio frequency identification (herein RFID) tag mountable to a product or product carrier, such as a pallet or container, and a plurality of interrogators spaced apart along the distribution path. Each interrogator of the plurality of interrogators cooperates in radio frequency (herein RF) communication with the RFID tag when the RFID tag is in proximity to each interrogator along the distribution path. Each interrogator interrogates the RFID tag during the RF communication so as to obtain unique data, unique to the RFID tag.
In one embodiment, each interrogator communicates the unique data to a central data base. The central database has associated with it a central database processor. The processor cooperates with the central database and communicates with the plurality of interrogators so as to obtain up-to-date data, including the unique data, from the RFID tag as the RFID tag progresses along the distribution path.
Distributed processors along the distribution path are also in communication with the central database processor so that the distributed processors may obtain feedback information and data from the central database no matter where the RFID tag is along the distribution path. This enables the distributed processors to obtain up-to-date product status data.
Each RFID tag and each interrogator comprises a transceiver and memory. The memory cooperates with the transceiver. In one aspect of the present invention the RFID tag may further comprise a data gathering sensor. The data gathering sensor may be an environmental status sensor such as a temperature sensor. In the preferred embodiment, the plurality of interrogators include at least one choke point interrogator, and may also include handheld or broadcast interrogators. The choke point interrogator interrogates for tag identifiers (ID""s) by means of time division multiplexing. The frame sizes within the time division multiplexing are adjusted by an interrogator processor calculating a collision rate. The frame sizes are optimized by an optimizing frame size adjustment based on the collision rate. The collision rate is calculated as between responses from the RFID tag in response to the interrogation from the choke point interrogator and responses from other RFID tags within a choke point communication range of the choke point interrogator.
The collision rate is determined by the choke point interrogator by the interrogator processor comparing:
(a) a cumulative first time period within the frame sizes wherein a signal strength detected by the choke point interrogator is increased so as to indicate transmission of responses from all the RFID tags, with
(b) a cumulative second time period within the frame sizes corresponding to known valid responses received by the choke point interrogator from all the RFID tags.
The interrogator processor calculates the optimizing frame size adjustment by increasing a total cumulative time within the frame sizes if the collision rate is higher than an optimal collision rate, and by decreasing the total cumulative time within the frame sizes if the collision rate is lower than the optimal collision rate. The optimal collision rate is, in one embodiment, between 10 to 40 percent and may be between 20 to 30 percent.
The choke point interrogator interrogates all the RFID tags within the choke point interrogator communication range in a rollcall until a statistical confidence level is obtained as determined by the choke point interrogator processor calculating a confidence level and the confidence level indicating that all the RFID tags have all successfully been identified.
Preferably the distributed processors spaced along the distribution path and the plurality of interrogators are located at corresponding producer, shipment, warehousing, and retailing locations. The communication of the distributed processors with the central database processor may advantageously be via the internet so as to allow feedback along the distribution path to locations upstream and downstream of a product""s location.